A little sunburn and seasickness might be the least of your worries once you set sail on that dream cruise.
More than 150 people, including 17 Americans, are currently confined to their cabins aboard a luxury cruise ship amid a suspected hantavirus outbreak that has left them stranded off the coast of West Africa.
At least seven people have fallen ill and three have died, prompting the World Health Organization to investigate whether the rare disease — usually spread through contact with infected rodents’ urine, feces or saliva — may be transmitting between humans.
And while this case is unusual, infectious disease outbreaks at sea are nothing new.
In the early days of COVID-19, nearly 3,700 passengers and crew on the Diamond Princess were locked down for two weeks off the coast of Japan. More than 700 were infected, and 10 died.
“This is really a textbook example of how respiratory viruses can spread very easily and efficiently in a confined space like a cruise ship,” Dr. Omer Awan, a physician and senior public health contributor for Forbes, told The Post.
So what makes cruise ships such hotbeds for disease — and how worried should travelers really be? The Post asked seven experts to find out.
Why are cruise ships prone to onboard outbreaks?
Cruise ship are an “ideal” environment for diseases to spread, according to immunologist and virologist Dr. Raymond Alvarez: “They are essentially dense, semi-closed ecosystems where thousands of people share space, food, air and surfaces over multiple days.”
That setup creates multiple pathways for illness. Buffets and shared dining spaces can fuel foodborne illness, while packed entertainment venues and tight living quarters make person-to-person transmission easier. High-touch surfaces — like railings and elevator buttons — become germ hubs, and even pools and hot tubs can play a role.
Then there’s the global mix of passengers. Thousands of travelers from different countries can bring pathogens with them — and take new ones home.
“There’s also crew rotations between voyages and they can carry germs between passenger groups, which is often why outbreaks can continue across several consecutive sailings of the same ship,” said Jason R. Margulies, a maritime lawyer with Lipcon, Margulies & Winkleman.
What illnesses commonly spread on cruise ships?
“The most common illnesses seen on cruise ships are usually those that affect our gut and colon, like norovirus,” Awan said. “This spreads easily through contaminated food, surfaces and of course person to person contact.”
Bacteria like E. coli and Salmonella are also frequent offenders, often tied to contaminated food or water.
“Microbes can easily travel person-to-person in the crowded conditions of a cruise ship,” said Dr. Jill Roberts, a molecular epidemiology expert at the University of South Florida College of Public Health. “If foods are contaminated, they can be ingested by 100s of guests, quickly creating large outbreaks,” she cautioned.
But it’s not just stomach bugs: Respiratory viruses like COVID-19 and the flu are also common because of shared airspaces and frequent social interactions, Awan noted.
And because many cruise passengers skew older — and often have underlying health conditions or weakened immune systems — outbreaks can take a more devastating toll than they might on land.
Which threats are less common?
“When cruises dock in tropical regions, passengers and crew can be exposed to diseases like Dengue fever or Zika virus infection during shore excursions,” Alvarez explained.
However, Alvarez noted, these illnesses typically don’t spread further onboard because they require a carrier, such as a mosquito, to pass them along.
Other risks include Legionnaires’ disease.
“It is not spread person-to-person, but contaminated water systems, including hot tubs, can aerosolize Legionella and cause severe pneumonia,” said Dr. Syra Madad, an infectious disease epidemiologist at the Harvard Belfer Center.
Skin infections — like cellulitis or hot tub folliculitis — can also crop up if pools and spas aren’t properly maintained.
And then there are the rarer but more serious threats, including varicella, measles and animal-transmitted diseases like hantavirus — since being on a cruise ship can “amplify unusual risks,” said Madad.
What is the worst-case scenario on a cruise ship?
“The worst case is a highly contagious airborne virus, something measles-like or a novel pandemic strain, spreading through a largely susceptible population,” Alvarez said. “In that setting, the close quarters and shared air on a ship can turn a single case into a ship-wide outbreak very quickly.”
It gets even more dangerous if people can spread the illness before showing symptoms, delaying detection and making containment harder.
Geography doesn’t help either.
“Modern cruise ships are no longer just sailing to the Caribbean, but many are headed to exotic ports of call that might complicate access to care,” said Dr. Suraj Saggar, chief of infectious disease at Holy Name Medical Center in New Jersey.
If a ship is far from shore with limited medical resources, treatment options can be scarce — and the outcomes worse.
How do cruise lines keep passengers safe — and what can you do?
Despite the risks, experts stress that cruise ships aren’t inherently dangerous, since operators implement precautions like sanitation programs, isolation protocols, enhanced cleaning and ventilation measures.
“That said, ships can still be efficient ‘mixing vessels,’” Madad noted. “So the risk is manageable depending on the type of infectious disease, but not zero.”
The good news is that a few simple steps can go a long way toward keeping you safe and healthy at sea.
First and foremost, make sure you’re up to date on your vaccines before you set sail, and ask your doctor whether any of your destination ports recommend special vaccinations for travelers.
“This could help prevent potentially serious illnesses such as hepatitis, typhoid and yellow fever,” Dr. Shalom Sokolow, an emergency medicine physician at Northwell’s Phelps Hospital, previously told The Post.
While on board, wash your hands regularly, especially after contact with others or using the bathroom, and before eating.
“If you are at a buffet, avoid communal platters where other guests have already reached in with their hands — it’s much better to use serving utensils,” Sokolow said.
“Additionally, be mindful of how long food may have been left out. Seafood and foods with mayonnaise are especially likely to harbor bacteria that cause food poisoning if left unrefrigerated too long.”
And, of course, wear sunscreen, stay hydrated, and make sure essentials like hand sanitizer, aloe vera, lip balm and a small medicine kit with over-the-counter pain relievers, antacids and allergy medications are at the top of your packing list.
Finally, the same rule that applies on land holds true on water: “If someone seems sick, better to avoid close contact,” Sokolow said.
